In a large pan, heat 1 tablespoon (15 milliliters) of the olive oil over medium low heat.
Add the spinach and cook, stirring often, until just wilted and a deep green.
Transfer the spinach to a colander and set aside to drain.
Place the pan over medium heat and add the remaining 1 tablespoon (15 milliliters) olive oil.
Add the onion and cook, stirring occasionally, until softened.
Stir in the garlic and cook until just fragrant, 30 seconds to 1 minute.
Crumble in the Italian sausage and cook, stirring occasionally, until browned and cooked through. Season with the salt, pepper, and nutmeg.
Remove the mixture from heat and set aside to cool slightly.
Place the cooled meat mixture in a large food processor.
Squeeze the moisture out of the cooked spinach and place in the food processor with the meat.
Add the grated Parmesan cheese and egg.
Blend the mixture until finely ground and combined.